1. Field of the Invention
This invention relates to an improvement of a conduction cooling type multistage collector for use in an electron beam tube such as a traveling wave tube or the like.
2. Description of the Prior Art
A collector for a traveling wave tube recovers a heat from an electron beam which results from an interaction of a high frequency wave in a slow-wave circuit. When the electron beam strikes against the collector, the kinetic energy which the electron possesses is converted to heat. As a result the collector reaches a high temperature. A multistage collector functions as a means for reducing the energy generated at this time to be as little as possible and for heightening an efficiency in the traveling wave tube.
The stage number of the collector to be adopted is generally 2 to 4 because of weight of the traveling wave tube and complication of the power source thereof. Also, a method of enabling an escape of the heat generated in the collector includes a natural air cooling, forced air cooling, conduction cooling or radiation cooling method or the like. In the case that the energy generated in the collector is relatively as small as several tens of Watts, the conduction cooling type is adopted.
FIG. 1 is a sectional view of a first embodiment of the prior conduction cooling type multistage collector, wherein the stage number of the collector is three. Three collector electrodes are in order arranged as the first, second and third collector electrodes 2, 3 and 4 from near a slow-wave circuit 1, said collector electrodes being electrically insulated with insulators 9, i.e. insulating porcelain 9 and the highest applied voltage being applied to the first collector electrode 2 and the gradually decreased applied voltage being applied to the second and third collector electrodes. Among the electron beams of which the interaction with the high frequency signal in the slow-wave circuit was completed, the slow speed electrons are caught with the first collector electrode 2 having the highest voltage and the high speed electrons are jumped in the innermost third collector electrode 4 with force. When the electrons impact on the collector electrodes, heat is generated. The heat generated in the collector electrodes is conducted through a cylindrical insulator 10 to a radiating block or heat dissipation block 7 and further to a base plate 8, in FIG. 1.
FIG. 2 shows a sectional view of a second embodiment of the prior collector structure wherein ring-shaped insulators 6 are in position held inside a metal vacuum envelope 11 and further collector electrodes 2, 3 and 4 are brazed inside the ring-shaped insulators 6.
FIG. 3 shows a sectional view of a third embodiment of the prior collector structure wherein first, second and third collector electrodes 2, 3 and 4 are mounted inside an integral insulator 12 with brazing. In this structure, there have been advantages that the collector is simple in the structure and is light-weight. However, there has been a risk that some problem in insulation is caused, since it is impossible to establish raised portions along the creeping surface of the insulating porcelain between the slow-wave circuit 1 and the first collector electrode 2 or between the first collector electrode 2 and the second collector electrode 3 and between the second collector electrode 3 and the third collector electrode 4.
In the structure of the first embodiment of FIG. 1 among the three prior structures as mentioned above, an insulation treatment became complicated since the collector electrodes form the vacuum envelope. In addition, since contacts between the collector electrodes and the cylindrical insulators and between the cylindrical insulators and the radiating block were mechanically made, there was a risk that heat resistance becomes easily high and thus the temperature rise in the collectors is caused. Also, in the structure of the second embodiment of FIG. 2, the insulation could be easily made but, with regard to heat dissipation, there was a defect that the ring-shaped insulator and the metal vacuum envelope cannot be directly brazed because of escaping the heat stress and thus the heat resistance becomes high at the portion. Moreover, in the third embodiment as shown in FIG. 3, since it is impossible to establish the raised portions along the creeping surface of the insulating porcelain between the collector electrodes, there was a risk that some problem in insulation is caused and there was a defect that the collector becomes large when trying to obtain sufficient insulation pressure resistance in direction of the axis.